1. Technical Field
This application generally relates to data storage, and more particularly to techniques used in connection with obtaining a specified lifetime for a data storage device.
2. Description of Related Art
Computer systems may include different resources used by one or more host processors. Resources and host processors in a computer system may be interconnected by one or more communication connections. These resources may include, for example, data storage devices such as those included in the data storage systems manufactured by EMC Corporation. These data storage systems may be coupled to one or more host processors and provide storage services to each host processor. Multiple data storage systems from one or more different vendors may be connected and may provide common data storage for one or more host processors in a computer system.
A host processor may perform a variety of data processing tasks and operations using the data storage system. For example, a host processor may perform basic system I/O operations in connection with data requests, such as data read and write operations.
Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units, disk drives, and disk interface units. Such storage devices are provided, for example, by EMC Corporation of Hopkinton, Mass. and disclosed in U.S. Pat. No. 5,206,939 to Yanai et al., 5,778,394 to Galtzur et al., U.S. Pat. No. 5,845,147 to Vishlitzky et al., and U.S. Pat. No. 5,857,208 to Ofek. The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels to the storage device and storage device provides data to the host systems also through the channels. The host systems do not address the disk drives of the storage device directly, but rather, access what appears to the host systems as a plurality of logical disk units, logical devices, or logical volumes (LVs). The logical disk units may or may not correspond to the actual disk drives. Allowing multiple host systems to access the single storage device unit allows the host systems to share data stored therein.
In connection with data storage, a variety of different technologies may be used. Data may be stored on disk devices (as described above), tape devices and flash memory devices, such as USB devices. Different storage technologies, such as a flash memory device, may fail primarily due to wear out or usage, such as after performing a certain number of write cycles to store data on the flash memory device. For example, a flash memory device that uses NAND flash memory and is an SLC (single level cell) device is expected to perform a specified number of writes to a cell. After performing the specified number of writes to the cell, that cell is expected to fail when attempting to subsequently write data thereto. As such, different techniques may be used when writing to the flash memory device. One technique is to use an error correction code (ECC) to allow recovery of data upon the occurrence of a write failure. Another technique is wear leveling which attempts to balance or evenly distribute writes across the physical device locations. Thus, when performing a write operation to a flash memory device, the write operation may be performed to a logical location on the device which is then mapped to a physical location on the device. With wear leveling and flash memory devices, the particular physical location for the same logical location may change in accordance with a mapping of virtual to physical locations in order to achieve the desired equal distribution of writes across physical locations of the device. The foregoing is one example of a data storage technology and cause of wear out where the device may be expected to fail after a specified amount of usage.